This invention relates to semiconductor manufacture and more particularly to an improved etchant for silica. Still more particularly the invention relates to the clean out of emitter openings following diffusion thereof by an etchant having a high preferential etch rate for doped silica.
In the past a typical etchant for cleaning out emitter openings was a buffered hydrofluoric acid consisting generally of a 15:1:4 mixture of 40% amonium fluoride, hydrofluoric acid, and water. Due to a low preferential etch rate as between the emitter oxide and the base oxide, great care was necessary to avoid etching out the sides of the base oxide to expose the base emitter junction of the transistor. Obviously if this base emitter junction was exposed to the metallization the transistor would be shorted between base and emitter.
It is an object of this invention to provide an improved etchant for semiconductor silica. A further object of the invention to provide an improved etchant for the emitter wash out process.
Further objects and advantages of the invention will be understood from the following complete description thereof.